Body fluid measuring apparatus with lancet and lancet holder used for the measuring apparatus

ABSTRACT

A body fluid measuring apparatus, comprising a main body ( 20 ) and a lancet holder ( 30 ) installed on the main body ( 20 ), the lancet holder ( 30 ) further comprising a lancet ( 31 ) capable of being moved for piercing to allow body fluid to be bled from skin (S) and a biosensor ( 36 ) introducing the bled body fluid for a specified measurement, wherein the biosensor ( 36 ) is moved in a specified direction by a sensor moving mechanism ( 40, 42 ).

TECHNICAL FIELD

The present invention relates to a body fluid measuring apparatusprovided with a lancet, which is capable of sampling and measuring bodyfluid by a single operation for checking a substance contained thereinsuch as the glucose concentration in blood (hereinafter referred to as“blood glucose level”). The present invention also relates to a lancetholder removably attached to such a body fluid measuring apparatus.

BACKGROUND ART

For diabetes treatment, the blood glucose level of a patient need bemaintained in a normal range. Thus, the management of the blood glucoselevel by the patient himself or herself is important. Particularly, forkeeping the blood glucose level in a normal range by insulin injection,measurement of the blood glucose level by the patient himself or herselfis essential.

A portable blood glucose level measuring apparatus used for such apurpose is already commercially available, an example of which isdisclosed in JP-A-4-357452. This blood glucose level measuring apparatusis used by inserting a disposable test piece provided with an enzymeelectrode into a main body. When the test piece is brought into contactwith blood as an analyte, a portion of the blood is introduced into areacting portion by capillary action, thereby generating an anodecurrent due to an enzyme reaction or an electrochemical reaction. In theapparatus, the anode current is converted to a blood glucose level,which is displayed.

In such a measuring apparatus as described above, the analyte, i.e.blood for contact with the test piece is generally sampled using aninstrument called lancet as disclosed in JP-A-9-266898 for example. Alancet is a tool used for making a small hole (or making a cut) on theskin of a fingertip, for example, of a patient. The blood drawn from thehole thus formed is brought into contact with a predetermined portion ofthe test piece. Thus, the self-measurement of the blood glucose levelcan be performed relatively easily.

However, the conventional self-measurement of the blood glucose level isinconvenient in that the lancet for sampling blood as an analyte isseparate from the measuring apparatus, so that the two tools need becarried. Moreover, it is necessary to separately perform the steps ofinjuring the skin with the lancet and of bringing the blood drawn fromthe cut into contact with the test piece. Therefore, there is still roomfor improvement in terms of the convenience of use. Particularly, inbringing the blood into contact with the test piece, a necessary amountof blood need be brought into contact with a predetermined portion ofthe test piece. Therefore, in the case where this step is performed byan untrained or week-sighted patient or where blood is drawn from anearlobe which cannot be observed by the patient himself or herself, itis not easy to bring the blood drawn from the cut into contact with thetest piece quickly and properly.

Further, the test piece is designed to suck blood from a hole at the tipend of the test piece into the biosensor provided in the reactingportion by capillary action. Therefore, 3 to 5 μl of blood need bebrought into contact with the test piece to ensure that a necessaryamount of blood reaches the reacting portion. If the amount of blood isinsufficient or if a sufficient amount of blood is not depositedappropriately on a small area surrounding the tip hole of the testpiece, the apparatus may suffer erroneous measurements. In particular,such a case is more likely to occur with respect to patients such asinfants and the elderly who tend to suffer insufficient drawing of bloodfrom a cut.

To solve the above-described problems, JP-A-10-28683 proposes a bloodglucose level measuring apparatus provided with a lancet. With thisapparatus, just by operating the lancet built in the apparatus to injurethe skin, the blood drawn from the skin can be measured by a biosensoralso built in the apparatus. However, the apparatus disclosed in thisgazette still has room for improvement in terms of convenience, because,in use, the lancet needle and the biosensor need be individually set atpredetermined positions in the apparatus.

For improving the convenience in use, the inventors of the presentinvention have proposed, in JP-A-10-166894, a lancet holder whichintegrates a lancet and a biosensor. According to this apparatus, thepatient's action needed for measurement is simplified, thereby enhancingthe convenience in use. Further, the reliability of measurement isenhanced while decreasing the amount of analyte necessary formeasurement. However, the reliability of measurement with a small amountof analyte of not more than 1.0 μl has not yet been satisfactory.

DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to provide a bodyfluid measuring apparatus provided with a lancet, which is capable ofrealizing high measurement reliability even with a small amount ofanalyte without deteriorating the convenience.

Another object of the present invention is to provide a lancet holderfor use in such a body fluid measuring apparatus.

A body fluid measuring apparatus according to a first aspect of thepresent invention includes a main body and a lancet holder forattachment to the main body. The lancet holder includes a lancet movablefor stabbing skin to draw body fluid, and a biosensor for introducingthe body fluid drawn to perform predetermined measurement. The biosensoris moved in a predetermined direction by sensor moving mechanism.

The lancet holder may be provided as a disposable article ofconsumption. For measurement, the user attaches the lancet holder to themain body. While holding the body fluid measuring apparatus so that thetip end of the lancet holder is pressed against the skin, the lancet ismoved back and forth by operating a lancet operating mechanism forexample. Such a movement of the lancet makes a cut on the skin, fromwhich body fluid (e.g. blood) is drawn. By keeping the holding state,the blood drawn is introduced into the biosensor for predeterminedmeasurement. According to the present invention, the sensor movingmechanism moves the biosensor so that the biosensor can locate moreclose to the blood drawn. As a result, even a small amount of blood of1.0 μl for example can be duly introduced into the reacting portion ofthe biosensor, which considerably enhances the reliability of themeasurement.

Preferably, the biosensor is shaped like a plate and internally formedwith a body fluid path having an inlet end. The biosensor is formed withan operative electrode and a counterpart electrode facing the body fluidpath at a position spaced from the inlet end. Since the biosensor isshaped like a plate as a whole, the body fluid path formed therein issmall in volume, which is suitable for the measurement of a small amountof analyte. Further, in the case where the operative electrode and thecounterpart electrode are formed on the upper surface of theplate-shaped biosensor, conduction is easily established between theseelectrodes and terminals of the main body.

Preferably, the body fluid measuring apparatus further comprises bodyfluid detecting means for detecting the drawn body fluid. The sensormoving mechanism moves the biosensor in the predetermined direction inresponse to a detection signal generated by the body fluid detectingmeans. In the case where the body fluid detecting means is provided,when the body fluid is not drawn, the biosensor is prevented fromunnecessarily advancing. This is advantageous for avoiding a measurementfailure.

According to one embodiment of the present invention, the body fluiddetecting means comprises a pair of conductance measuring electrodesfacing the body fluid path at the inlet end of the biosensor. The bodyfluid is detected by sensing conduction established between theconductance measuring electrodes due to the body fluid. Since theconductance measuring electrodes can be formed similarly to theoperative electrode and the counterpart electrode and at the same timeas forming such electrodes, the manufacturing cost can be reduced.Further, such a structure is convenient for establishing electricalconnection between the conductance measuring electrodes and terminals ofthe main body.

According to another embodiment of the present invention, the body fluiddetecting means is non-contact detection means for detecting existenceof the body fluid without contacting the body fluid drawn. With thisstructure, when a sufficient amount of body fluid is not drawn, thebiosensor is not contaminated. Therefore, the biosensor together withthe lancet holder can be reused so that the wasting can be prevented.The non-contact detection means comprises a light source (e.g. a lightemitting diode) for emitting light toward the skin, and a lightreceiving element (e.g. a photodiode) for receiving reflected light fromthe drawn body fluid.

Preferably, the biosensor comprises a base plate having an upper surfaceon which the operative electrode and the counterpart electrode areformed, a pair of spacers spaced from each other and disposed on thebase plate, and a cover plate laminated on the spacers to bridge thespacers. The body fluid path is defined between the spacers.

Preferably, the body fluid path is formed with a reactive reagent layer.

Preferably, the sensor moving mechanism comprises an eccentric camdriven by a motor for rotation, and the eccentric cam pushes an edge ofthe biosensor.

Preferably, the main body includes a plurality of terminals for slidablycontacting a plurality of electrodes formed on an upper surface of thebiosensor, an electronic circuit connected to the plurality ofterminals, a lancet operation mechanism for moving the lancet forstabbing, and a display for displaying a measurement result. It ispreferable that each of the terminals preferably comprises an elasticconnector pin.

Preferably, the biosensor is held inclined so that one edge is closer tothe skin than an opposite edge, and the biosensor is movable along aninclined movement path. In this case, it is preferable that the sensormoving mechanism acts on the opposite edge of the biosensor.

The biosensor includes a first electrode facing the body fluid path atthe inlet end, and a second electrode facing the body fluid path at anend opposite to the inlet end. The filling of the body fluid path withthe body fluid is detected by measuring conductance between the firstelectrode and the second electrode. In this case, for decreasing thenumber of electrodes, it is preferable that the second electrode is oneof the operative electrode and the counterpart electrode.

A lancet holder according to the second aspect of the present inventioncomprises a lancet which is movable for stabbing skin to draw bodyfluid, and a biosensor for introducing the body fluid drawn to performpredetermined measurement. The biosensor is supported for movement in apredetermined direction.

Other features and advantages of the present invention will becomeclearer from the detailed description given below with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall view illustrating a body fluid measuring apparatusaccording to the present invention.

FIG. 2 is a sectional view taken along lines II—II in FIG. 5,illustrating a lancet holder in which a lancet and a biosensor areretreated.

FIG. 3 is a sectional view similar to FIG. 2, illustrating a lancetwhich is advanced and a biosensor which is retreated.

FIG. 4 is an enlarged sectional view illustrating a lancet which isretreated and a biosensor which is advanced.

FIG. 5 is a bottom view of the lancet holder.

FIG. 6 is a schematic perspective view showing the internal structure ofthe main body.

FIG. 7 is a plan view of the biosensor.

FIG. 8 is a sectional view taken along lines VIII—VIII of FIG. 7.

FIG. 9 is an exploded perspective view of the biosensor.

FIGS. 10-12 illustrate the operation of the biosensor.

FIG. 13 is a flowchart illustrating an example of process forcontrolling the sampling and measuring of the body fluid.

FIG. 14 is a sectional view showing a principal portion according toanother embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowwith reference to the accompanying drawings.

As shown in FIGS. 1 through 3, a body fluid measuring apparatus 10according to a preferred embodiment of the present invention is usedwith a lancet holder 30 fitted to a cylindrical tip end 21 of a mainbody 20. The main body 20 has an outer surface provided with a display22 and may incorporate a small speaker (not shown) for vocally reportingthe measurement result to the user. Further, the main body 20incorporates a lancet operation mechanism for advancing a lancet 31 heldby the lancet holder 30, a sensor moving mechanism for advancing abiosensor 36, and an electronic circuit 33 (See FIG. 6) such as amicrocomputer.

The lancet operation mechanism for advancing the lancet 31 comprises apushing rod 23 projecting from the rear end of the main body 21 formanual pushing by the user, and a connection rod 32 connected to thepushing rod 23 for movement following the pushing rod 23. The sensormoving mechanism for advancing the biosensor 36 comprises a motor 40 andan eccentric cam 42 fixed to a rotational shaft 41 of the motor 40.

FIGS. 2 and 5 illustrate an example of lancet holder 30. The illustratedlancet holder 30 has a cap-like configuration comprising a cylindricalwall 34 and a bottom wall 35 partially closing the end of thecylindrical wall 34. The cylindrical wall 34 and the bottom wall 35 areformed by molding a resin. The cylindrical wall 34 has an inner diametercorresponding to the outer diameter of the cylindrical tip end 21 of themain body 20 for easy attachment and detachment relative to thecylindrical tip end 21. The cylindrical wall 35 has a lower end 34 awhich, in use, comes into contact with the user's skin S.

The cap-shaped lancet holder 30 incorporates the lancet 31 and thebiosensor 36. The bottom wall 35 includes a thin-walled portion 35 afrom which a cylindrical housing 35 b stands. The cylindrical housing 35b has an upper end closed with a lid 35 c. The lid 35 c is formed with acentral hole 35 d.

The lancet 31 includes a guide shaft 31 a slidably fitted into thecentral hole 35 d, a flange 31 b formed at the lower end of the guideshaft 31, and a stabbing needle 31 c projecting from the flange 31 b.The guide shaft 31 a and the flange 31 b are formed by molding a resinand integral with each other. The stabbing needle 31 c, which is formedof a metal, is inserted integrally together with the resin molding. Thelancet 31 is normally biased toward a retreated position (the positionat which the flange 31 b contacts the lid 35 c) shown in FIG. 2 by anelastic member 37 arranged in the housing 35 b in contact with theflange portion 31 b. At the retreated position, the upper end of theguide shaft 31 a projects inwardly from the lid 35 c, whereas thestabbing needle 31 c retreats from the lower end 34 a of the cylindricalwall 34. The thin-walled portion 35 a of the lancet holder 30 is formedwith a round hole 35 f. The stabbing needle 31 c advances and retreatsthrough the round hole 35 f.

In the illustrated embodiment, the elastic member 37 is a compressioncoiled spring formed of a metal or a resin. Alternatively, the elasticmember may be formed of a resilient material such as foamed urethane. Inthe case where the elastic member 37 is made of foamed urethane, thestabbing needle 31 c is embedded in the foamed urethane when the lancet31 is at the retreated position so that the stabbing needle is lesslikely to be contaminated. Further, the elastic member 37 may be a leafspring integrally formed on the guide member 31 a formed of a resin.

The plate-like biosensor 36 is slidably supported, as inclined, by thebottom wall 35 of the lancet holder 30 adjacent to the lancet 31. Asshown in FIGS. 7 and 9, the biosensor 36 has an elongated rectangularconfiguration. The biosensor 36 includes an insulating base plate 361, apair of plate-shaped spacers 362, 362′ laminated on the insulating baseplate 361, and a plate-shaped cover 363 further laminated on theplate-shaped spacers 362, 362′. The insulating base plate 361 has anupper surface formed with a pair of conductance measuring electrodes 36a, 36 a′, an operative electrode 36 c and a counterpart electrode 36 d.The insulating base plate 361, the two plate-shaped spacers 362, 362′and the plate-shaped cover 363 define a body fluid path 36 b (See FIG.8). Part of the conductance measuring electrodes 36 a, 36 a′, part ofthe operative electrode 36 c and part of the counterpart electrode 36 dface the body fluid path 36 b. The body fluid path 36 b accommodates areaction reagent portion 36 e.

The biosensor 36 may be manufactured as follows. First, as shown in FIG.9, an elongated rectangular base plate 361 is prepared from aninsulating resin sheet having a thickness of 0.2 mm for example.

Subsequently, conductance measuring electrodes 36 a, 36 a′, an operativeelectrode 36 c, and a counterpart electrode 36 d are formed on an uppersurface of the base plate 361 as film strips extending longitudinally ofthe base plate 36 a by screen-printing a graphite ink. The conductancemeasuring electrodes 36 a, 36 a′, the operative electrode 36 c, and thecounterpart electrode 36 d may be alternatively provided by forming afilm of noble metal such as gold, palladium or platinum by vapordeposition to entirely cover the upper surface of the base plate 361 andthen etching the metal film into a predetermined pattern.

Subsequently, a pair of rectangular spacer plates 362, 362′ are disposedon the base plate 361 while keeping a spacing therefrom which isslightly larger than the spacing between the two conductance measuringelectrodes 36 a and 36 a′. Each spacer plate 362, 362′ may be a resinplate having a thickness of 0.2 mm for example and fixed to the baseplate 361 with a double-sided adhesive tape for example. The body fluidpath 36 b may be 1.0 mm in width, 3 mm in length and 0.2 mm in depth(which is equal to the thickness of the spacer plates 362, 362′) forexample.

Then, as clearly shown in FIG. 8, a reactive reagent layer 36 e isformed in the body fluid path 36 b by the dispensing method for example.In the case where the biosensor 36 is used for measuring the bloodglucose level, the reactive reagent layer 36 e contains glucose oxidasewhich is an oxidization enzyme, and potassium ferricyanide as amediator.

Subsequently, as shown in FIG. 9, a rectangular cover plate 363 isattached to cover the spacer plates 362, 362′, thereby completing thebiosensor 36. As a result, the body fluid path 36 b is upwardly closedby the cover plate 363. However, the body fluid path 36 b is open at theopposite ends thereof for allowing body fluid (blood) to enter the bodyfluid path 36 b due to capillary action for reaction with the reactivereagent layer 36 e. The body fluid path 36 b of the above dimensions hasa volume of 0.6 μl, which is found by 1.0 mm×3 mm×0.2 mm. Bysubtracting, from this value, 0.2 μl which is the approximate solidvolume of the reactive reagent layer 36 e, it is found that the bodyliquid flow path 36 b has an extremely small net volume of about 0.4 μl.

As clearly shown in FIG. 2, the plate-like biosensor 36 is supported, asinclined, by the bottom wall 35 of the lancet holder 30 so that thestabbing needle 31 c is located adjacent to the conductance measuringelectrodes 36 a, 36 a′. The biosensor 36 is so inclined that the sideformed with the conductance measuring electrodes 36 a, 36 a′ is closerto the user's skin than the counterpart electrode 36 d.

The biosensor 36 is slidably movable to approach the stabbing needle 31c by the sensor moving mechanism 40 which will be described later. Asshown in FIGS. 4 and 5, the bottom wall 35 of the lancet holder 30 isformed with a round hole 35 e for fitting to the lower end of therotational shaft 41 of the motor 41. Thus, when the lancet holder 30 isattached to the main body 20, the rotational center of the eccentric cam42 is precisely determined. Further, the bottom wall 35 of the lancetholder 30 is formed with a pair of arcuate openings 36 f (See FIG. 5)sandwiching the biosensor-supporting region. By the provision of theopenings 36 f, a negative pressure generating mechanism for example maybe provided in the main body for exerting a negative pressure to theskin while holding the cylindrical wall 34 of the lancet holder 30 incontact with the skin S.

As shown in FIGS. 4 through 7, the cylindrical tip end 21 of the mainbody 20 is provided with four pin connectors 25 a, 25 b, 25 c, 25 d eachhaving a tip end projecting from the cylindrical end 21 into the lancetholder 30. The pin connectors 25 a-25 d individually and elasticallycontact the exposed portions (i.e. portions which are not covered withthe cover 363) of the electrodes 36 a, 36 a′ 36 c 36 d of the biosensor36. The pin connectors 25 a-25 d are connected to the electronic circuit33 (See FIG. 6). The electronic circuit 33, which may comprise amicrocomputer, has a function of determining the value of an analytesuch as the blood glucose level from the current generated due to enzymereaction or electrochemical reaction in the biosensor 36 by utilizingthe calibration curve, a function of displaying the determined value atthe display 22 of the main body 20, and a function of controlling thesensor moving mechanism 40 for moving the biosensor 36.

In the illustrated embodiment, the eccentric cam 42 driven by the motor41 for rotation includes a bevel surface. When the lancet holder 30 isattached to the body 20, the bevel surface comes into contact with anedge of the biosensor 36 (the edge which is opposite to the edge formedwith the conductance measuring electrodes 36 a, 36 a′). The degree ofeccentricity of the cam 41 is set in accordance with the stroke formoving the biosensor 36 (e.g. 0.1-0.5 mm). The rotational initialposition of the cam 42 is detected by a rotary encoder 43.

In use, the body fluid measuring apparatus 10 having the above structureoperates in the manner described below.

The lancet holder 30 is supplied as a disposable article of consumption.In using the body fluid measuring apparatus 10, the user attaches thelancet holder 30 to the cylindrical portion 21 of the main body 20 (SeeFIG. 1). Since the lancet holder 30 is shaped like a cap in theillustrated embodiment, the attaching operation can be performed easily.As shown in FIG. 2, by the attachment of the lancet holder 30, theconnector pins 25 a, 25 b, 25 c, 25 d on the side of the main body 20automatically come into contact with the electrodes 36 a, 36 a′, 36 c,36 d of the biosensor 36.

Subsequently, with the lower end 34 a of the cylindrical wall 34 of thelancet holder 30 pressed against an appropriate portion of the user'sskin such as a fingertip or an earlobe, the pushing portion 23 is pusheddown. As a result, the pushing rod 32 within the main body 20 pushes theguide shaft 31 a of the lancet 31 to advance the lancet 31 against theelastic force of the elastic member 37 until the pushing rod 32 comesinto contact with the lid 35 c of the lancet holder 30. At this time,the stabbing needle 31 c of the lancet 31 passes adjacent to the inletof the body fluid path 36 b of the biosensor 36 to project from thelower end 34 a of the cylindrical wall 34 by a predetermined length (thestate shown in FIG. 3). When the pushing portion 23 is relieved, thepushing rod 32 is restored to its original position by the elastic forceof the spring. Further, due to the elastic force of the elastic member37, the lancet 31 also returns to its retreated position where thestabbing needle 31 c retreats from the lower end 34 a of the cylindricalwall 34 (the state shown in FIG. 2).

The projection of the stabbing needle 31 c makes an appropriate cut onthe skin S to draw blood B, which is introduced to the inlet of the bodyfluid path 36 b of the biosensor 36 by capillary action. At the momentwhen the blood enters the inlet of the body fluid path 36 b of thebiosensor 36, current flows across the paired conductance measuringelectrodes 36 a, 36 a′ so that a signal is generated due to the changeof the conductance. In response to the signal, the motor 41 drives thebiosensor 36 through the eccentric cam 42 for forward movement. Thisprompts the blood to be sucked into the body fluid path 36 b.

As described above, since the net volume of the body fluid path 36 b inthe biosensor 36 is extremely small and the biosensor 36 is advancedtoward the blood, the body fluid path 36 b is reliably filled with asmall amount of blood. Therefore, blood can be introduced into the bodyfluid path 36 b in an amount just necessary for the measurement simplyby conducting the above operation while keeping the lancet holder 30pressed against the skin S for a predetermined period of time. Thus, itis not necessary to visually monitor the amount of blood drawn. Asdescribed before, a negative pressure generating mechanism such as asuction cylinder may be provided in the main body to apply a negativepressure to the skin S through the openings 36 f of the lancet holder30. In such a case, a cut is formed on the skin in a congestive state bythe stabbing needle 31 c so that a required amount of blood is morereliably drawn.

Next, with reference to the operational figures of FIGS. 10-12 and theflowchart of FIG. 13, the operation of the apparatus will be describedin more detail by showing an example of the controlling operation by theelectronic circuit 33.

First, when the switch of the main body is turned on, the position ofthe eccentric cam 42 is initialized (S01). At this time, as shown inFIGS. 2 and 10, the biosensor 36 is located at the most retreatedposition. The initialized state is detected by the rotary encoder 43.

In this state, the user conducts the bleeding operation by holding theapparatus with the lancet holder 30 pressed against the skin S andoperating the lancet 31 in the above-described manner (FIG. 3). Asdescribed before, since the inlet of the body fluid path 36 b of thebiosensor is arranged close to the lancet 31 in advance, the blood Bdrawn from the skin contacts the inlet of the body fluid path 36 b. Thisstate is detected due to a change in the resistance between the twoconductance measuring electrodes 36 a, 36 a′. Specifically, whether thebleeding has occurred or not is determined by measuring the resistancebetween the pin connectors 25 a and 25 b corresponding to theconductance measuring electrodes 36 a, 36 a′ (S02).

If bleeding is not detected within a predetermined period of time (S02:NO, S03: YES), a failure warning is given vocally or by displaying (S04)to urge the user to retry.

If the bleeding is detected (S02: YES), the bleeding is reported vocallyfor example (S05), and the eccentric cam 42 is driven to advance thebiosensor 36 (S06). Thus, as shown in FIGS. 4 and 11, the biosensor 36is moved so that the inlet of the body fluid path 36 b projects into thedrawn blood. As a result, the blood is reliably introduced into the bodyfluid path 36 b due to capillary action. As described before, thebiosensor 36 is so inclined that the inlet of the body fluid path 36 bis closer to the skin whereas the opposite side is farther from theskin. This arrangement prevents the reverse surface of the advancedbiosensor 36 from contacting the skin, thereby preventing the blood fromreaching the reverse surface of the sensor. Thus, the waste of blood canbe prevented.

Subsequently, it is determined whether the body fluid path 36 b isfilled with the blood (S07). As shown in FIG. 11, this may be performed,for example, by measuring the resistance between one of the conductancemeasuring electrodes 36 a, 36 a′ and the counterpart electrode 36 d.This is because, when the body fluid path 36 b is filled with blood, acurrent flows across these electrodes.

If the body fluid path 36 b is not filled with the blood within apredetermined period of time (S07: NO, S08: YES), a failure warning isgiven vocally or by displaying (S09) to urge the user to retry.

If it is determined that the body fluid path 36 b is filled with blood(S07: YES), a notice is given vocally or by displaying that theapparatus may be removed from the skin S for example (S10). Thus, themeasurement starts in S11 (See FIG. 12), and the result is displayed(S12) to terminate the process.

When the reactive reagent layer 36 e is dissolved in the blood in thebody fluid path 36 b in the biosensor 36, an enzyme reaction starts, asrepresented by the formula (1) given below. As a result, potassiumferricyanide contained in the reactive reagent layer 36 e is reduced tocumulatively produce potassium ferrocyanide which is a reduced-typeelectron carrier.

The amount of potassium ferrocyanide is proportional to theconcentration of the substrate, i.e., the glucose concentration in theblood. The reduced-type electron carrier produced in a predeterminedtime is oxidized by the electrochemical reaction represented by thefollowing formula (2).Fe(CN)₆ ⁴⁻→Fe(CN)₆ ³⁻+e⁻  (2)

The electronic circuit 33 in the main body 20 of the measuring apparatus10 performs calculation to determine the glucose level (blood glucoselevel) based on the detected operative electrode current and displaysthe result on the LCD display 22 provided at the main body 20.

In this way, with the body fluid measuring apparatus 10 according to thepresent invention, it is possible to perform body fluid measurement suchas blood glucose level measurement just by performing the preparationstep of placing the lancet holder 30 at a predetermined portion of themain body 20 and the bleeding step of advancing the lancet 31 whilekeeping the tip end of the lancet holder 30 pressed against a fingertipor earlobe of the patient. Therefore, it is not necessary to separatelyperform, after the bleeding step, a measuring step by using othermeasuring instrument than the lancet. Further, since the biosensor 36 isadvanced after the bleeding, the measurement can be reliably performedeven with a small amount of blood.

As is clear from the above description, the gist of the presentinvention lies in that the body fluid measuring apparatus 10 comprises adisposable lancet holder 30 which integrates both a biosensor 36 and alancet 31 and which is attached to the main body 20, whereby the lancet31 causes bleeding of body fluid (blood) toward which the biosensor 36is advanced for causing the sensor 36 to be internally filled with thebleeding fluid. Therefore, all the modifications within such a spiritare included in the scope of the present invention. Although some of thepossibilities of modification have already been described, othermodifications are also possible, as described below.

In the above embodiment, the biosensor 36 progresses from the retreatedposition to the advanced position in one step. However, the biosensor 36may progress in two steps. Specifically, the biosensor 36 is initiallyheld at the retreated position which is spaced from the lancet 31 by acertain distance. After the stabbing operation by the lancet 31, thebiosensor 36 may be advanced to a detection position for detecting theblood drawn. Then, after the detection of the blood, the biosensor 36may be further advanced to the most advanced position.

In the above embodiment, blood is detected by measuring the conductance(resistance) between the conductance measuring electrodes 36 a, 36 a′ atthe inlet of the body fluid path 36 b of the biosensor 36. However, theblood may be detected by non-contact detection means. For example, asshown in FIG. 14, the main body 20 may be provided with opticaldetection means including a light emitting element 51 for emitting lighttoward the skin S and a light receiving element 52 for receiving lightreflected by the skin S. Thus, whether or not blood is properly drawnmay be determined by measuring the amount of light of particularwavelength range (e.g. red light) received by the light receivingelement 52. In this case, the light emitting element 52 may be a lightemitting diode (LED) or a laser generator. As another example of opticaldetection means, the blood image on the skin may be captured by a smallCCD camera and the size of a region having a particular color may bemeasured and computed to detect the bleeding state. Further, instead ofthe optical detection means, detection means utilizing ultrasonic wavesmay be employed. In the case where such non-contact detection means isused, the bleeding can be confirmed without contaminating the biosensor,thereby avoiding wasting of the biosensor.

According to the present invention, however, the drawing of the bloodneed not necessarily be confirmed. Therefore, on the assumption that thepushing of the lancet 31 inevitably causes bleeding, the biosensor 36may be advanced when a predetermined period of time has passed after thepushing of the lancet 31.

In the illustrated embodiment, the lancet operation mechanism includes apushing portion 23 for manual operation and a pushing rod 32 movabletogether with the pushing portion 23 so that the lancet 31 normallybiased toward the retreating direction by the elastic member 37(compression coil spring) is pushed forward (See FIGS. 2 and 3).Alternatively, though not illustrated, a lancet 31 may constantly belatched at a retreated position as elastically biased in the advancingdirection so that the lancet 31 hits the skin by a resilient elasticforce when the latch is manually released.

Further, as the sensor moving mechanism for moving the biosensor 36, usemay be made of a solenoid, a piezo-electric element, shape-memory alloy,or a spring instead of the motor-driven eccentric cam 42 of the aboveembodiment.

In the illustrated embodiment, the elastic pin connectors 25 a-25 dprovided in the main body 20 are electrically connected to theelectrodes of the biosensor 36 when the lancet holder 30 is attached tothe main body 20. Instead of this, pin connectors, which are normallyretreated within the main body 20, may project from the main body 20 forcontact with the electrodes of the biosensor in response to theattachment of the lancet holder 30 to the main body 20.

In the illustrated embodiment, the body fluid measuring apparatus 10 isdescribed as an apparatus for measuring the blood glucose level.However, the measurement is not limited to the blood glucose level.Further, the specific design of the lancet holder 30 and the biosensor36 may be varied in various ways. For example, the biosensor 36 may beprovided with a reagent pad which exhibits color reaction uponcontacting an analyte (body fluid), and the degree of the color reactionis optically measured. In this case, the detection of the body fluidbleeding from the skin is preferably performed optically. After theexistence of the body fluid is detected, the biosensor is moved to aposition for contacting the body fluid. After the body fluid is dulyintroduced to the reagent pad, the degree of reflection of the lightemitted from the light source to the reacting portion is opticallymeasured.

1. A body fluid measuring apparatus comprising: a main body; and alancet holder for attachment to the main body; wherein the lancet holderincludes a lancet movable for stabbing a skin to draw body fluid, and abiosensor for introducing the drawn body fluid to perform predeterminedmeasurement; and wherein a sensor moving mechanism including a motor isfurther provided for moving the biosensor in a predetermined direction.2. The body fluid measuring apparatus according to claim 1, wherein thebiosensor is shaped like a plate and internally formed with a body fluidpath having an inlet end, the biosensor being formed with an operativeelectrode and a counterpart electrode facing the body fluid path at aposition spaced from the inlet end.
 3. The body fluid measuringapparatus according to claim 2, further comprising body fluid detectingmeans for detecting the drawn body fluid, the sensor moving mechanismmoving the biosensor in the predetermined direction in response to adetection signal generated by the body fluid detecting means.
 4. Thebody fluid measuring apparatus according to claim 3, wherein the bodyfluid detecting means comprises a pair of conductance measuringelectrodes facing the body fluid path at the inlet end of the biosensor,the body fluid being detected by sensing conduction established betweenthe conductance measuring electrodes due to the body fluid.
 5. The bodyfluid measuring apparatus according to claim 3, wherein the body fluiddetecting means is non-contact detection means for detecting existenceof the body fluid without contacting the drawn body fluid.
 6. The bodyfluid measuring apparatus according to claim 5, wherein the non-contactdetection means comprises a light source for emitting light toward theskin, and a light receiving element for receiving reflected light fromthe drawn body fluid.
 7. The body fluid measuring apparatus according toclaim 2, wherein the biosensor comprises a base plate having an uppersurface on which the operative electrode and the counterpart electrodeare formed, a pair of spacers spaced from each other and disposed on thebase plate, and a cover plate laminated on the spacers to bridge thespacers, the body fluid path being defined between the spacers.
 8. Thebody fluid measuring apparatus according to claim 2, wherein the bodyfluid path is formed with a reactive reagent layer.
 9. The body fluidmeasuring apparatus according to claim 2, wherein the biosensor includesa first electrode facing the body fluid path at the inlet end, and asecond electrode facing the body fluid path at an end opposite to theinlet end, filling of the body fluid path with the body fluid beingdetected by measuring conductance between the first electrode and thesecond electrode.
 10. The body fluid measuring apparatus according toclaim 9, wherein the second electrode is one of the operative electrodeand the counterpart electrode.
 11. The body fluid measuring apparatusaccording to claim 1, wherein the sensor moving mechanism comprises aneccentric cam driven by the motor for rotation, the eccentric campushing an edge of the biosensor.
 12. The body fluid measuring apparatusaccording to claim 1, wherein the main body includes a plurality ofterminals for slidably contacting a plurality of electrodes formed on anupper surface of the biosensor, an electronic circuit connected to theplurality of terminals, a lancet operation mechanism for moving thelancet for stabbing, and a display for displaying a measurement result.13. The body fluid measuring apparatus according to claim 12, whereineach of the terminals comprises an elastic connector pin.
 14. The bodyfluid measuring apparatus according to claim 1, wherein the biosensor isheld inclined relative to a longitudinal axis of the lancet, thebiosensor being movable along an inclined movement path.
 15. The bodyfluid measuring apparatus according to claim 14, wherein the sensormoving mechanism acts on the opposite edge of the biosensor.
 16. Alancet holder comprising: a lancet which is movable for stabbing a skinto draw body fluid; and a biosensor for introducing the body fluid drawnto perform predetermined measurement; wherein the biosensor is heldinclined relative to a longitudinal axis of the lancet for movementalong a movement path.
 17. A body fluid measuring apparatus comprising:a main body; and a lancet holder for attachment to the main body;wherein the lancet holder includes a lancet movable for stabbing a skinto draw body fluid, and a biosensor for introducing the drawn body fluidto perform predetermined measurement; wherein a sensor moving mechanismis further provided for moving the biosensor in a predetermineddirection; and wherein the biosensor is shaped like a plate andinternally formed with a body fluid path having an inlet end, thebiosensor being formed with an operative electrode and a counterpartelectrode facing the body fluid path at a position spaced from the inletend.
 18. A body fluid measuring apparatus comprising: a main body; and alancet holder for attachment to the main body; wherein the lancet holderincludes a lancet movable for stabbing a skin to draw body fluid, and abiosensor for introducing the drawn body fluid to perform predeterminedmeasurement; wherein a sensor moving mechanism is further provided formoving the biosensor in a predetermined direction; and wherein the mainbody includes a plurality of terminals for slidably contacting aplurality of electrodes formed on an upper surface of the biosensor, anelectronic circuit connected to the plurality of terminals, a lancetoperation mechanism for moving the lancet for stabbing, and a displayfor displaying a measurement result.
 19. A body fluid measuringapparatus comprising: a main body; and a lancet holder for attachment tothe main body; wherein the lancer holder includes a lancet movable forstabbing a skin to draw body fluid, and a biosensor for introducing thedrawn body fluid to perform predetermined measurement; wherein a sensormoving mechanism is further provided for moving the biosensor in apredetermined direction; and wherein the biosensor is held inclinedrelative to a longitudinal axis of the lancet, the biosensor beingmovable along an inclined movement path.